Conventionally, when performing deep-drawing, bending, cutting, or the like to a metal material, using a press-forming device, it is usual to carry out actual production after determining appropriate forming conditions, namely, processing conditions such as the shape of metal molds, lubricating conditions, forming speed, blank holding force, the temperature of metal molds and work, etc. for every metal material in advance by trial production through experience, or through experiment, or by simulation or the like using a finite-element method.
Various metal materials being a raw material can be plates, pipes, bars, wires, powder or grains, and the like obtained through multiple processes of melting-smelting-casting-rolling-heat treatment-secondary processing and so on from raw material or scraps, and there inevitably exists some extent of deviation in mechanical properties in a product due to fluctuation of chemical components, or fluctuation of processing conditions such as uneven temperatures.
Accordingly, even when appropriate forming conditions are determined in advance as described above, occurrence of forming defect may arise due to differences in formability according to material positions or production lot numbers. In order to avoid this defect, an execution of quality control during material production process is performed more severely. However, such severity may lead to a material cost increase, and may not be recommendable.
Moreover, even when the mechanical characteristics of the raw material are identical, occurrence of forming defect may arise due to environmental fluctuation during processing such as temperature change of metal mold caused by continuous operation, abrasion of metal mold, fluctuation of atmospheric temperature or humidity.
As a countermeasure against these disadvantages, various inventions for a press-forming method to control processing conditions according to metal material or conditions of a metal mold have been disclosed. For example, Japanese Patent Application Laid-open No. Hei 7-266100 describes is a device to control air pressure in an air cylinder to carry out press-forming under an appropriate blank holding force. This is described as being performed by determining in advance a relation between a physical quantity such as a shape of press material and its mechanical property, chemical property, a laminate layer property of plating or the like, and surface conditions such as oil quantity or the like; and an appropriate blank holding force from which prescribed press quality is obtained; and by determining the appropriate blank holding force according to actual physical quantity from the above-described relation.
Japanese Patent Application Laid-open Nos. Hei 5-285700 and Hei 6-246499 describe a device which adjusts press conditions based on machine information and metal mold information peculiar to a press machine. Japanese Patent Application Laid-open Nos. Hei 7-265957, Hei 10-128451 and Hei 8-300048 describe various methods to adjust to prescribed bending angles in a bending process using a press brake.
Japanese Patent Application Laid-open Nos. Hei 7-266100, Hei 5-285700 and Hei 6-246499 provide descriptions which are generally aimed at controlling blank holding force based on material characteristics, information peculiar to a machine, and metal mold information. However, since lubrication characteristics, especially with metal molds, may vary from one moment to the next by the synergistic effect of the fluctuation of material characteristics and the fluctuation of machine and mold conditions, it may be difficult to estimate the force in advance.
The description of Japanese Patent Application Laid-open Nos. Hei 7-265957, Hei 10-128451 and Hei 8-300048 are generally aimed at adjusting the processing conditions according to the state of deformation during processing of the work in a bending process, but it is difficult to measure complicated three-dimensional shape on the spot in drawing or cutting. Further, since material is cramped with a metal mold during drawing or cutting, problems may exist in measuring the material shape precisely.
One of the objects of the present invention is to overcome and/or address the above-described problems, and to provide a way to perform satisfactory press-forming while compensating deviation of various material characteristics and environmental fluctuation during processing.